<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <meta http-equiv="X-UA-Compatible" content="ie=edge">
    <title>Document</title>
    <style>
        ul {
            list-style: none;
        }
        
        .menu>li {
            float: left;
        }
    </style>
</head>

<body>
    <ul class="menu">
        <li>开源软件</li>
        <li>企业版</li>
        <li>搞笑版</li>
        <li>
            我的马云
            <ul>
                <li>二级菜单1</li>
                <li>二级菜单2</li>
                <li>二级菜单3</li>
                <li>二级菜单4</li>
            </ul>
        </li>
    </ul>
</body>

</html>